1. Field of the Invention
The present invention relates to a shank assembly pivotally mounted to a support and held in position with a link which can include a release device which relies on near center locking action, but will release under excessive loads.
2. Prior Art
Various spring trip assemblies that use near center latching type links, and which do not depend upon floating, nor upon high lift parallel linkage mechanisms have been advanced. For example U.S. Pat. No. 2,565,668 shows a spring type standard for cultivators which includes a compression spring, and a near center pivoting link arrangement.
An additional near center type linkage arrangement is shown in U.S. Pat. No. 2,944,613 in a cultivator assembly, but this device also includes some "float" for the shovel before the linkage trips.
Undercutters themselves have been known for a number of years, but generally operate with rigid shanks. The undercutter sweeps are very large, and may have a width at the back of in the range of three feet and models made by others have widths up to five to seven feet. A device forming prior art has been made by Noble Cultivators Limited of Alberta, Canada, with rigid shanks, and with very wide sweeps. A further device is the "Nichols Tool Bar Shank" which was made similar to the Noble shank, and constitutes prior art that goes back into the early 1950's. It is a rigid shank for the wide undercutter sweeps.
The undercutters generally travel from 2" to 5" below the ground surface and are designed to minimize the surface disturbance.